Add support for parallel runs

ct/go/util/constants.go

Index: ct/go/util/constants.go
diff --git a/ct/go/util/constants.go b/ct/go/util/constants.go
index d76167365ab784f8d6eaa67426efce60496603b3..a287b1b1f29b6c0ecf0d6dbe6487572f3f908295 100644
--- a/ct/go/util/constants.go
+++ b/ct/go/util/constants.go
@@ -187,8 +187,9 @@ const (
 	WEBHOOK_SALT_MSG = `For prod, set this file to the value of GCE metadata key webhook_request_salt or call webhook.MustInitRequestSaltFromMetadata() if running in GCE. For testing, run 'echo -n "notverysecret" | base64 -w 0 > /b/storage/webhook_salt.data' or call frontend.InitForTesting().`
 
 	// Swarming constants.
-	SWARMING_DIR_NAME = "swarming"
-	SWARMING_POOL     = "CT"
+	SWARMING_DIR_NAME     = "swarming"
+	SWARMING_POOL         = "CT"
+	BUILD_OUTPUT_FILENAME = "build_remote_dirs.txt"
 	// Timeouts.
 	BATCHARCHIVE_TIMEOUT = 10 * time.Minute
 	XVFB_TIMEOUT         = 5 * time.Minute
@@ -199,6 +200,8 @@ const (
 	CAPTURE_SKPS_FROM_PDFS_ISOLATE = "capture_skps_from_pdfs.isolate"
 	RUN_LUA_ISOLATE                = "run_lua.isolate"
 	CHROMIUM_ANALYSIS_ISOLATE      = "chromium_analysis.isolate"
+	CHROMIUM_PERF_ISOLATE          = "chromium_perf.isolate"
+	BUILD_REPO_ISOLATE             = "build_repo.isolate"
 )
 
 type PagesetTypeInfo struct {